1. The Field of the Invention
The present invention relates to the manufacture of semiconductor devices, and more particularly to the formation of contact structures such as contacts and vias that provide electrical contact to underlying structures. The present invention is particularly useful in the formation of high aspect ratio contact structures.
2. The Relevant Technology
As feature sizes in integrated circuits decrease, new technologies are required to produce functional structures with ever smaller dimensions. Methods for forming contact structures, which must often be formed in very high aspect ratio spaces (i e., ratio of depth to width &gt;1), have become increasingly emphasized in semiconductor fabrication engineering.
Contact structures are typically formed by first creating a contact space in the form of a hole or trench in a dielectric layer, then filling the contact space with a conductive material by any number of methods, typically including sputter deposition, to form the contact structure.
Pure titanium or pure tungsten or other refractory metals are often currently used as a barrier layer between an aluminum-containing fill material and the inner surfaces of a contact space. While these films function well as barrier layers, they react with aluminum, which reaction has been found to inhibit the mobility along the inner surfaces of the contact space of the subsequently deposited aluminum-containing fill material. Such mobility has been found to play a significant role in adequately filling the contact space.
In filling high aspect ratio contact spaces, the fill material can often deposit more heavily at the opening of the contact space, so that the opening of the contact space is closed off before the bottom of the contact space is adequately filled. The likelihood of such problems only increases with the increasing aspect ratio. Methods to provide improved contact filling resulting in improved contact structures are thus needed.